Relative speed indicating system



y 1950 G. H. RENDEL 2,506,106

RELATIVE SPEED INDICATING SYSTEM Filed March 2, 1949 20/ INVENTOR.

GEORGE H. RENDEL ATTORNEY Patented May 2, 1950 RELATIVE SPEED INDICATING SYSTEM George H. Rendel, Pittsburgh, Pa., assignor to Carnegie-Illinois Steel Corporation, a corporation of New Jersey Application March 2, 1949, Serial No. 79,205

8 Claims. 1

This invention relates to a relative speed indicating system and more particularly to such a system for indicating the relative speeds of the rolls of a tandem rolling mill. On stretch rolling mills in which the roll stands are arranged in tandem, part of th reduction of gage of the strip being rolled is produced by the tension exerted on the strip. For a given setting of the rolls the amount of tension depends on the relative speeds of adjacent roll stands. The amount of reduction produced on the strip is also a function of the tension. Therefore, to insure that the strip is being reduced the desired amount, it is necessary to maintain the tension and relative speeds of the rolls constant. For that reason it is necessary to know the amount of tension exerted on the strip between the various roll stands. This is sometimes done by mounting a movable roll between each pair of roll stands for deflecting the strip out of the direct path between the roll stands. The amount of pressure exerted on this deflecting roll is measured to determine the tension on the strip. While such tension indicators are satisfactory in many cases it is impossible to use them in some installations. It is desired to space the roll stands as close together as possible in order to obtain the maximum benefits of the stretch rolling process. Therefore, in many instances the rolls are so closely spaced that the strip is hidden from view between the stands and there is not sufficient room to mount the tension indicator described above.

It is therefore an object of my invention to provide a system for indicating the relative speeds of the rolls of a tandem rolling mill which in turn is an indication of the tension developed between the roll stands.

This and other objects will be more apparent after referring to the following specification and. attached drawing in which:

The single figure is a schematic view of my device.

Referring more particularly to the drawing, the reference character S indicates a strip passing through the roll stands l, 2, 3 and 4 of a tandem rolling mill. The roll stands l, 2, 3 and 4 are driven by the motors 5, E, l and 8, respectively, which are connected through lines 9 and It to a, D. C. power source. Field windings H, l2, l3 and M of motors 5, 6, l and 8 are arranged in series with rheostats l5, l6, l1 and 18, respectively, and are energized through lines 19 and 20 connected to a constant potential D. C.

power source.

Associated with the roll stands I, 2, 3 and 4 are the tachometer generators 2|, 22, 23 and 24, respectively, which are driven at a speed proportional to the peripheral speed of the rolls of the associated roll stand. As shown in the drawing the tachometer generators are connected directly to a roll of the associated roll stand. Rheostats '25, 2t, 22 and 28 are connected in shunt with the generators 2!, 22, 23 and 24, respectively. The negative poles of generators 2 I, 22, 23 and 24 are connected by means of the connector wire 29. The rheostats 25, 26, 2'! and 28 are provided with adjustable contact arms 30, 3|, 32 and 33, respectively. Associated with the roll stands l, 2, 3 and i are polarized voltmeters 34, 35, 36 and 3?, respectively. Meters 34, 35 and 3! are the center zero type and are preferably calibrated for a scale of 20-0-20 volts and meter 35 is of the left hand zero type. One of the leads of each of the meters 34, 35, 36 and 3! is connected to the movable contact arms 3%, 3!, 32 and 33, respectively. The other lead of meter 35 is connected to the wire 29. The other lead of each of the meters 3 3 and 36 is connected to the contact arm 3| of rheostat 26. The other lead of meter 3'! is connected to the adjustable arm 32 of rheostat 27. Mill stand No. 2 may be considered the master or pilot mill which has a substantially fixed speed for a given rolling schedule and the meter 35 will be referred to as the master or standard meter. The mill stand No. 2 need not be selected as the master mill, but it is desirable that the master will be one that is close to the center of the rolling mill. For example, in a five-stand mill the No. 3 mill would be the standard and the hook-up for the meters for stands 2, 3, 4 and 5 would be the same as for the hook-up of stands I, 2, 3 and 4, respectively, as shown in the drawing and described above. The meter for stand No. I would have one terminal connected to the adjusting arm of the shunt rheostat of mill No. I and the other arm connected to the adjusting arm of the shunt rheostat of mill No. 2. In other words, regardless of the number of stands, one of the leads of each of the voltmeters will be connected to the movable contact arm associated therewith and the other lead of the standard meter will be connected to the common lead connecting the generators. The other lead of each of the vcltmeters adjacent the standard meter will be connected to the movable contact arm of the resistance associated with the standard voltmeter. The other lead of the remaining voltmeters, regardless of the number, will be connected to the movable contact arm of the voltmeter adjacent thereat 100, 200, 400 and 800 feet per minute, respectively, the field rheostats l5, l6, 1! and [8 will be adjusted to obtain the desired speeds, as indicated on the meters 38, 39, es and M, respectively. The No. 2 mill will be considered the master or pilot mill having a substantially fixed speed for a given rolling schedule. The relative speed and consequently the relative drafts of mills No. 1 and No, 3 are indicated and controlled with reference to the speed of No. 2 mill. The speed or draft of No. 4 mill is referred to that of No. 3 mill in a manner similar to that in which the draft of No. 3 mill is referred to the speed of No. 2 mill. With the speed of roll stands I, 2, 3 and 4 set at 100, 200, 400 and 809 feet, respectively, the rheostat 25 is adjusted until the meter 35 indicates, for example, 160 volts, thus impressing a potential of 100 volts between the common negative wire 29 and the contact arm Bl. Meter 3 3 is then calibrated by adjusting rheostat 25 until the meter 34 indicates zero. In like manner rheostats 27 and 28 are adjusted until meters 36 and 31 also indicate zero. When the above adjustments are completed, potential from the negative leads of generators 21, 22, 23 and 24 to each of the contact arms 3B, 3 l, 32 and 33, respectively, is 100 volts so that all of the meters 34, 36 and 31 will indicate zero deflection when meter 35 indicates 100 volts.

As long as there is zero deflection on the draft meters 34, 36 and 3?, the operator will know that the tandem mill is running satisfactorily. If the speed of mill No. 1 is reduced 10%, the voltage from tachometer generator 2| will also decrease 10% and the potential drop across rheostat 25, which is directly proportional to the voltage of generator 2!, causes the voltage from the negative tachometer generator lead to the contact arm 36 to be reduced by 10%, This results in a potential of 10 volts across the terminals of meter 34 so that the meter will indicate 10 volts which corresponds to a 10% deviation in the speed of No. 1 mill. In the same manner an increase in speed of No. 1 mill of 10% will cause the meter 34 to indicate a 10% deviation in the speed in the opposite direction. The draft meters being center zero polarity Sensitive instruments will indicate both direction and magnitude of the deviation. In order to correct the above conditions the operator will adjust rheostat E5 to increase or decrease the speed of No. 1 mill until the meter 34 again reads zero. If desired, equipment may be provided to automatically change the speed of the rolls in response tothe reading of the draft meters. In like manner change of speed of N0. 3 mill will cause a corresponding change in voltage from its tachometer generator 23, thus resulting in a deflection of meter 36 to'indicate the direction and magnitude of the deviation. Meter 3'! is actuated by referring the speed of No. 4 mill to No. 3 mill in a manner similar to which the meter 36 is actuated by referring the speed of No. 3 mill to the No. 2 mill. In case No. 2 mill reduces speed, the impressed potential on meter 35 will be reduced proportionally causing meters 34 and 36 to deflect toward the fast side, thus indicating that mills No. 1 and No. 3 are operating at relatively faster speeds than the No. 2 mill. This condition can be corrected by increasing the speed of No. 2 mill.

While one embodiment of my invention has been shown and described, it will be apparent that other adaptations and modifications may be made without departing from the scope of the following claims.

' I claim:

1. A system for indicating the relative speeds of the rolls in the stands of a tandem rolling mill comprising a tachometer generator associated with each of said stands and connected to be driven at a speed proportional to the peripheral speed of the rolls in the associated stand, an adjustable resistance connected in shunt with each of said generators, a movable contact arm for each of said resistances, means connecting one of the common poles of all of said generators, a polarized voltmeter for each of said stands, one of the leads of each voltmeter being connected to the associated movable contact arm, the other lead of an intermediate voltmeter being connected to the common connecting means, and the other lead of each of the voltmeters adjacent the said intermediate voltmeter being connected to the movable contact arm of the resistance associated with the intermediate voltmeter.

2. A system according to claim 1 in which the resistances are adjusted so that all the voltmeters except said intermediate voltmeters will read zero when the speed relationship between the various stands is that desired.

3. A system for indicating the relative speeds of the rolls in the stands of a tandem rolling mill comprisin a tachometer generator associated with each of said stands and connected to be driven at a speed proportional to the peripheral speed of the rolls in the associated stand, an adjustable resistance connected in shunt with each of said generators, a movable contact arm for each of said resistances, means connecting one of the common poles of all of said generators, a polarized voltmeter for each of said stands, one of the leads of each voltmeter being connected to the associated movable contact arm, the other lead of an intermediate voltmeter bein connected to the common connecting means, the other lead of each of the voltmeters adjacent the said intermediate voltmeter being connected to the movable contact arm of the resistance associated with the intermediate voltmeter, and the other lead of the remaining voltmeters being connected to the movable contact arm of the resistance associated with the voltmeter adjacent thereto.

4. A system according to claim 3 in which the resistances are adjusted so that all the voltmeters except said intermediate voltmeter will read zero when the speed relationship between the various stands is that desired.

5. A system for indicating the relative speeds of motors arranged in tandem comprising a tachometer generator associated with each of said motors and connected to be driven at a speed proportional to the speed of the associated motor, an adjustable resistance connected in shunt with each of said generators, a movable contact arm for each of said resistances, means connecting one of the common poles of all of said generators, a polarized voltmeter for each of said tachometer generators, one of the leads of each voltmeter be ing connected to the associated movable contact arm, the other lead of an intermediate voltmeter being connected to the common connecting means, and the other 1ead of each of the voltmeters adjacent the said intermediate voltmeter being connected to the movable contact arm of the resistance associated with the intermediate voltmeter.

6. A system according to claim 5 in which the resistances are adjusted so that all the voltmeters except said intermediate voltmeter will read zero when the speed relationship between the various motors is that desired.

7. A system for indicating the relative speeds of motors arranged in tandem comprising a tachometer generator associated with each of said motors and connected to be driven at a speed proportional to the speed of the associated motor, an adjustable resistance connected in shunt with each of said generators, a movable contact arm for each of said resistances, means connecting one of the common poles of all of said generators, a polarized voltmeter for each of said tachometer generators, one of the leads of each voltmeter being connected to the associated movable contact arm, the other lead of an intermediate voltmeter being connected to the common connecting means, the other lead of each of the voltmeters adjacent the said intermediate voltmeter being connected to the movable contact arm of the resistance associated with the intermediate vo1tmeter, and the other lead of the remaining voltmeters being connected to the movable contact arm of the resistance associated with the voltmeter adjacent thereto.

8. A system according to claim 7 in which the resistances are adjusted so that all the voltmeters except said intermediate voltmeter will read zero when the speed relationship between the various motors is that desired.

GEORGE H. RENDEL.

Name Date Umansky Aug. 11, 1936 Number 

